Reduce Repo Assist schedule from hourly to 4x daily (#19459)

Change schedule from 'every 1h' to 'every 6h' to reduce run frequency
while still maintaining adequate coverage.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: T-Gro

.github/workflows/repo-assist.lock.yml

@@ -14,7 +14,7 @@ description: |
   Always polite, constructive, and mindful of the project's goals.
 
 on:
-  schedule: every 1h
+  schedule: every 6h
   workflow_dispatch:
   slash_command:
     name: repo-assist